1. Field of the Invention
This invention relates to image reproducing equipment used in a copying machine, etc., in which an original document image is read out by the use of a solid-state imaging device (CCD etc.) or other opto-electric conversion means to obtain an electrical image signal, and then the image is reproduced.
2. Description of the Prior Art
A device in which the original image is read out by a solid-state device such as CCD, used to modulate a laser beam to form a reproduced image on a photosensitive body is known. In this case the processing such as modulation is made easier by converting a read out signal into a binary digital signal. Accordingly the number of brightness levels were limited to two and the reproduction of intermediate tones was a difficult task.
There was an attempt to reproduce the image by using a large number of bits per picture element (pel) in order to express the intermediate portion of the analog level read out signal. However, it was unsuitable for a copying machine since the processing speed was reduced extremely and since the structure became complicated. It was impossible in the examples of the prior art described above to obtain a copy good gradation qualities from an original which is poor in gradation or a copy by increasing the contrast of a desired portion of the original.